Reduced auditory evoked gamma band response and cognitive processing deficits in first episode schizophrenia

• Published in: The world journal of biological psychiatry 2015-08, Vol.16 (6), p.387-397
• Main Authors: Leicht, Gregor, Andreou, Christina, Polomac, Nenad, Lanig, Clarissa, Schöttle, Daniel, Lambert, Martin, Mulert, Christoph
• Format: Article
• Language: English
• Subjects: auditory; EEG; first episode; gamma; schizophrenia
• ISSN: 1562-2975; 1814-1412
• DOI: 10.3109/15622975.2015.1017605

Objectives. Gamma-band oscillations (e.g., the early auditory evoked gamma-band response, aeGBR) have been suggested to mediate cognitive and perceptual processes by driving the synchronization of local neuronal populations. Reduced aeGBR is a consistent finding in patients with schizophrenia and high-risk subjects, and has been proposed to represent an endophenotype for the illness. However, it is still unclear whether this reduction represents a deficit in sensory or cognitive processes, or a combination of the two. The present study investigated this question by manipulating the difficulty of an auditory reaction task in patients with first-episode schizophrenia and healthy controls. Methods. A 64-channel EEG was recorded in 23 patients with first-episode schizophrenia and 22 healthy controls during two conditions of an auditory reaction task: an easy condition that merely required low-level vigilance, and a difficult condition that placed significant demands on attention and working memory. Results. In contrast to healthy controls, patients failed to increase aeGBR power and phase-locking in the difficult condition. In patients, aeGBR power and phase-locking indices were associated with working memory deficits. Conclusions. The observed results confirm the applicability of aeGBR disturbances as a stable endophenotype of schizophrenia, and suggest a cognitive, rather than sensory, deficit at their origin.